[Graham]

And finally the comments made by you all,

Qman
I agree that the winners cars should be scrutineered for their hidden secrets and I will make a point of getting my magnifier glass out and even do some photos (as I want to know myself)   when the cars come back hopefully if DHL are on form this afternoon.

There are some general points though
Tyres are fundamental  requirement for keeping cars on the tracks, and some cars had tyres which were very uneven, or so hard that they were probably only good for the track the car was normally used on. And one in particular the Elise was too narrow (although perfectly in scale), it was good for a couple of laps but collected dust from the track very easily which disrupted it longer running times performance compared to almost all the other cars.
Guides needed to appropriate choice for the plastic tracks they were used on, shallow slot rails and narrow slot rail widths (even so on the modern Scalextric Sport track), meant that cars fitted with thick, long deep wood guides just were at times impossible to get round.
Braids need to appropriate to the guide being used, obviously with such a shallow slot for the classic SCX/scalex tracks, older Scalextric cars fitted with the blue guides where disadvantaged if fitted with the original wire braids, as they were only 5mm deep anyway, the wire took another 1mm off the depth. Those few which used the blue guides but changed the original wire braids for copper soft braids faired much better as the copper braids are much thinner allowing a greater depth of the guide in the slot.
Ballast - some cars entered had no ballast fitted at all, and consequently struggled more so on the Hill climb type more bumpy type tracks than other cars. Others if they did have ballast, certainly was no where near enough for these more difficult tracks.

As for why the Beamers did so badly, contact Paul Cooper his Honda Civic ran very well and they essentially are much the same car, in fact these BTCC scalex cars had the advantage of having the slot motor slightly recessed lower on the chassis on these cars, which as scrutineer I perhaps should have not allowed as they were of marginally lower track clearance than the 2mm allowed compared to other scalex models, but abit of discretion was used as these Scalex cars were fixed chassis.

one more post to come